Portable electronic devices with text entry capabilities are increasing in usage. These devices are being built in smaller sizes each year. For many of these devices, such as cellular phones, models that are small in size are perceived as desirable by consumers. Cellular phone manufacturers have responded to this, and produce a variety of cellular phones that are small relative to earlier models, with some models being smaller than the size of a user's palm.
Cellular phones have a number of features that require a user to input alphanumeric characters. A user may, for example, enter alphanumeric text in the name field of a phone list maintained in the phone. A user may also use a cell phone to send text messages via short messaging service (SMS) technology. To do this, a user generally inputs alphanumeric characters into the phone. Typically, a numeric keypad is used to enter alphanumeric characters, where the number of alphanumeric characters exceeds the number of numeric input keys.
A technique generally used to enter alphanumeric characters into a phone uses a standard alphabetic arrangement illustrated in FIG. 1. In this method a cellular phone has two data entry modes, a numeric mode and an alphanumeric mode. In the numeric mode, activation of the data entry keys represents numeric digits. The numeric digits are determined from the correspondence between each data entry key and the numeric digit associated with that key. In a standard telephone, activation of data entry keys in numeric mode generates dual tone multifrequency (DTMF) signals in accordance with an industry standard.
When operating in the alphanumeric mode, single activation of a data entry key is interpreted as a user selection of the first letter in the sequence of letters that are assigned to the particular data entry key. Similarly, when a data entry key is activated twice by a user, this is interpreted as a selection of the second letter in the sequence of letters associated with that particular data entry key. A timeout threshold is used to determine when selection of a character is complete. If a period of time equal to the timeout threshold follows the activation of a key without a subsequent activation of a key, the selection of the character is considered to be completed. Also, if the user activates a first key followed by an activation of a different key, the activation of the second key is considered to be the beginning of the selection of a new character.
With this method, a user may activate a key one, two, three, or four times in order to select a particular letter of the alphabet. Multiple activations of keys increase the time required to enter text using the keypad.
In addition to use of the keys to enter alphanumeric data, letters on keys assist users in entering telephone numbers or other numeric data. Some telephone numbers are represented by mnemonic phone numbers, in which at least part of the phone number is specified by the use of letters, to assist in memorization of the number. For example, 1-800-ABCDEFG is equivalent to 1-800-2223334, when a user activates each key once for each number or letter in the mnemonic phone number.
Because entry of alphanumeric characters on a limited keypad is less efficient than on a full sized keyboard, a mechanism for improving the efficiency is desirable. Changes to increasing efficiency can be problematic because users are familiar with the standard key mapping. Also, the use of mnemonic telephone numbers is a further consideration.
There is, therefore, a need in the art for an improved device and method for entering alphanumeric data in a portable communications device.